This invention relates to a disc cartridge liner for wiping off the dust deposited on a recording disc in a disc cartridge.
The recording disc, such as an optical disc, a magnetic disk or a magneto-optical disc, is composed of a disc-like substrate and a signal recording layer provided on the major surface of the disc substrate. Conventionally, such a recording disc is housed in a disc cartridge 31 in the form of casing, as shown in FIG. 1, to be handled as a disc cartridge for preventing damages to the recording disc due to deposition of dust and contact by fingers and for facilitating its handling.
That is, the disc cartridge is constituted by a recording disc 32 rotatably housed in the cartridge 31.
The recording disc 32 has a central portion 32 a thereof as a portion to be chucked, to which a disc hub 34 presenting chucking function is secured with an adhesive ring 33 between them, so that the portion to be chucked is held by a disc recording/reproducing apparatus for recording/reproducing information signals onto/from the recording disc 32. The recording disc 32 also has a signal recording surface 32b for writing/reading out information signals on the peripheral side of the central portion 32a.
The cartridge 31 housing the recording disc 32 therein is composed of a pair of an upper half 35 and a lower half 36. The upper half 35 and the lower half 36 are abutted to contact each other for housing the recording disc 32. In the major surfaces of the upper and lower halves 35, 36, recording/reproduction openings 37 are formed for exposing at least part of the signal recording surface 32b of the recording disc 32 to outside. The lower half 36 is also provided with a chucking opening 38 for exposing the disc hub 34 mounted on the recording disc 32 to outside. Thus, the recording disc 32 is held to the disc hub 34 through the chucking opening 38 by the disc recording/reproducing apparatus, so that information signals are written onto and/or read out from the signal recording surface 32b through the recording/reproduction openings 37. The disc cartridge is provided with a shutter member 39 which closes the recording/reproducing openings 37 when the disc cartridge is not in use, to prevent intrusion of dust into the cartridge 31 for protecting the recording disc. The shutter member 39 is caused to be slidable along one side edge of the lower half 36.
In addition, liners 40 are provided in the disc cartridge, for removing the dust which has intruded in the cartridge 31 and deposited on the signal recording surface 32b of the recording disc 32. The liners 40, formed of an unwoven fabric, are attached to major surfaces on the side of housing the recording disc 32 of the upper and lower halves 35, 36, so as to sandwich the recording disc 32 from the major surfaces thereof in contact with the recording disc 32. Consequently, if the recording disc 32 is rotated, the dust deposited on the signal recording surface 32b of the recording disc 32 is wiped off by the liners 40 and taken in between fibers of the liners. Thus, damages to the signal recording surface 32b caused by a magnetic head contacting the surface with dust deposited thereon can be avoided.
Normally, the liner 40 is composed of a single fiber selected from polypropylene, polyester, nylon and rayon, or blended fibers thereof blended at an appropriate proportion.
Rayon, above all, is a type of regenerated cellulose fiber having a petal-shape cross section as shown in FIG. 2. This petal acts advantageously for raising the dust deposited on the sheet surface, exhibiting excellent dust wipe-off effect.
Meanwhile, though rayon exhibits satisfactory cleaning effect, it is very fragile and tends to be lowered in strength by moisture. In addition, since rayon is high in hygroscopicity, it has its coefficient of friction with the recording disc affected by humidity in the operating environment, and has a high rate of contraction due to moisture absorption.
Thus, if this rayon is singly entangled, the resulting entangling body has insufficient durability, and low dimensional precision when punched out into a liner shape. Therefore, it is difficult to form a dimensionally precise production from rayon. Also, since rayon has its slidability affected by humidity when slid in contact with the recording disc, it is difficult to obtain stable cleaning effect. For these reasons, rayon is blended with thermoplastic fibers, such as polyester, polypropylene and nylon, and is thus improved in dimensional stability, frictional stability and strength, to be used for the liner.
However, if rayon is blended with the thermoplastic fiber to form a liner, a greater coefficient of friction of the thermoplastic fiber causes an intense frictional heat to be generated in its contact with the recording disc. The frictional heat softens and abrades the liner, generating abrasion particles. The resulting abrasion particles are deposited onto the recording disc, inducing errors in recording and reproduction. In addition, since the thermoplastic fiber in general is low in water absorption property and high in electrical resistance, it often causes static electricity to be generated in contact with the recording disc, obstructing rotation of the recording disc.